The present invention relates to a method for the continuous, quasi-static and contactless determination of the width of hot rolled products inside a rolling mill train, preferably of hot broad band by means of diode line cameras on which the two side edges of the illuminated rolling mill product are projected, and a device for carrying out the method, consisting of diode line cameras arranged above the rolling mill product and fluorescent lamps arranged underneath the rolling mill product.
Methods and devices for determining the width of rolling mill products are known, see "Stahl und Eisen" 1977, No. 4, pp. 147/150. The known device consists of two diode line cameras of which one each is arranged above a train edge of a rolling band running on a roller bed. Underneath the roller bed which is arranged in a pickling device placed ahead of a cold rolling mill, light bands for illuminating the band or its edges are provided. The diode line cameras can be moved in the top portion of a frame on a shaft by means of a motor in the axial direction. With this known device with which the width of cold rolled band is measured, the cameras must be moved in a disadvantageous manner before taking a measurement from an initial position to a measuring position. Movable measuring devices which must operate under difficult conditions such as increased temperatures in an atmosphere containing dust and vapors, are only conditionally operational. However, it is not possible to secure the sensitive apertures of the diode line cameras and the transport device against these influences because a continuous gap-like opening in the apparatus housing is required for the measurements. In addition, the known device uses for illuminating the bands to be measured direct-current fed luminous lamps which result in further disadvantages. In particular, to prevent the dark zones occurring in direct-current fed luminous lamps after a short operation interval, special switching devices for polarity reversal are required, since only the fluroescent lamps conventionally operated with alternating current attain a sufficiently high intensity of illumination for the given purpose. Also, with the known device, measurements are performed with very small time intervals, where the measuring cycle depends on the bandwidth and lasts approximately 1 msec for the widest band. The electrical charge placed on the diodes of the diode line cameras is relatively small.
There also is known a measuring device for measuring the width of hot rolled material, (see "Stahl und Eisen" 1977, No. 19, pp. 927/932) where the inherent radiation of the hot rolled material is used as light source for each of the diode line cameras fixedly located on both sides and above a roller bed. Aside from the fact that measuring results are obtainable only if the rolled material has a temperature of more than 550.degree. C. and water accumulations, tinder spots, etc. carried on hot rolled material lead to erroneous measurements, the known arrangement includes an additional camera to detect vertical movements of the band to be measured and to correct the measured width. Such an arrangement cannot be used for most operational applications, since roller beds on which the rolled material is moved have lateral restrictions through guide rulers and an observation of the transported band of the additional lateral camera is not possible.
Accordingly, it is an object of the present invention to provide a method and a device for determining the width as described and to avoid the disadvantages of the known methods and devices. The width of hot rolled material, particularly in the temperature range from 400.degree. to 1200.degree. C. is to be measured under the difficult conditions of a hot rolling mill and in a measuring cycle whose period is independent of the bandwidth. Constant full functioning ability is to be maintained and it is to be ensured that the width of bands which are not transported precisely in the middle of a roller bed is measured correctly and accurately.
Another object of the present invention is to provide an arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide a method and device, as described, which may be readily maintained in service and which has a substantially long operating life.